The intensity, beam pattern and beam aim point of vehicle front lamp assemblies are regulated because of the impact they have on various safety issues. Sufficient light is needed under a variety of driving conditions so as to allow the operator of a vehicle to see the road being traveled upon as well as hazards that may present themselves. The concern with adequate lighting is balanced by safety concerns for others.
An operator of a vehicle may be blinded by the front lamps of an oncoming vehicle. Similarly, a pedestrian may be blinded by the front lamps of an oncoming vehicle. Typically, the blinding is a result of direct glare. That is, glare resulting from light emitted from the lamp assemblies directly into the eyes of the operator or pedestrian (also referred to as disability glare and discomfort glare). Concern for this type of glare has resulted in regulations regarding the shape of the upper portion of the emitted beam as well as the illumination level in that upper portion.
The problem of direct glare has been addressed in a number of ways. The most significant manner of addressing this issue is the use of two different beam patterns, high beam and low beam. Depending upon the situation, such as other traffic in the vicinity, the vehicle operator selects the desired beam in order to decrease the light emitted by the front lamp assemblies (“low beam”) or to increase the light emitted by the front lamp assemblies (“high beam”). Multiple beams may be realized by using multiple light sources and/or moving a cutoff shield, a reflector, the light source and or the lens of the lamp assembly.
While the problem of glare for other operators and pedestrians has been given a significant amount of attention, the problem of glare to the operator of the vehicle from the vehicles own front lamps has remained largely unaddressed. Glare to the operator of a vehicle, or reflective glare, typically occurs as a result of wet, snow-covered or icy road conditions. In this environment, light from the lowest portion of the emitted light beam, used to light the road immediately in front of the vehicle or the foreground area, can be reflected back at the vehicle, blinding the operator.
The problem of reflective glare can be addressed to some extent by the use of shaped light beams, either by using a square reflector or manufacturing a lamp assembly with a permanent foreground shield that eliminates foreground lighting. However, these approaches unnecessarily eliminate foreground lighting under conditions wherein reflective glare is not a concern (i.e. dry road conditions). Moreover, if a reflective foreground shield is used, the problem of direct glare may be exacerbated. By reflecting a beam back through the main reflector, the emitted beam may not be uniform since the light reflected from the shield will typically not be emitted in a direction parallel to light that has not been reflected by the shield.
The potential impact of any solution to the reflective glare issue should take into consideration potential design limitations. By way of example, designers of sports cars frequently attempt to design vehicles with a low-slung, sleek appearance. Such designs may require a headlamp to be mounted at or very near the upper portion of the front of the vehicle, with little if any freeboard above the headlamp. This presents a challenge when reducing reflective glare for headlamps wherein the upper portion of the light beam reflected off the reflector is the primary contributor to reflective glare. In such headlamps, any additional hardware cannot be mounted near the upper part of the headlamp.
Therefore, a need exists for an automotive lighting system that provides for the reduction and/or elimination of foreground lighting when reflective glare conditions exist (i.e. when roads are icy, snow-covered or wet), but that also allows more intense illumination of the foreground area when reflective glare conditions do not exist (i.e. when roads are dry). It would be beneficial if the lighting system did not require additional equipment to be placed above the headlamp assembly. It would be further beneficial if the system operated with a variety of light source, shield and reflector configurations.